Abrasive wheel



UNITED STATES PATENT OFFICE.

HENRY nonnmrowan. or nuem r annsnnw Yonx, assmn'on THE CAR'BOBUNDUM COMPANY, OF NIAGARA FALLS, NEW YORK, LL OOBPO T1011 OF PENNSYLVANIA.

No Drawing.

To all whom it may concern:

Be it known that I, IIENRY Roann'r Power, a citizen ,of the United States, residing at Niagara Falls, in the county of Niagara and State of New York, have invented a new and useful Improvement in Abrasive Wheels, of

whichthe following is a specification.

My invention relates to abrasive wheels, and especially to an improvement in open or porous abrasive wheels in which the bond employed to hold together the particles of abrasive material is a silicate.

My invention is designed to greatly increase the efliciency, of such wheels by an improvement in their construction.

Abrasive wheels to which my invention relatesare made up of an abrasive material such as carborundurn or carbid of silicon; an aluminous abrasive commonly known as emery, aloxite or corundum, held together by a ceramic bond. In such wheels the'bond may be silicate of soda which is mixed with the abrasive grains together with certain other chemical compounds and heated to a temperature suflicient to cause a reaction between the silicate and these other chemicals. This gives a hard porous mass in which the abrasive grains are held securely in place; Such wheels are known as silicate of soda wheels. Or the bond may be clay, together with other mineral silicates, such as feldspar, etc. In such wheel the bond and gram are mixed and heate in a kiln until the bond melts or fuses. This gives upon cooling a hard,- porous mass and such a wheel is known commercially as a vitrified wheel.

Both of the types of wheel above described are porous, and in the grindin process these pores become filled wit particles of the material being ground, thus cover ng over the sharp cutting edges of the abrasive grains and preventing proper clearance for the cutting ints. Also in the grinding process the ai'ifrasive particles become worn, lose their sharp ed become too smooth for effective work. The face of such a wheel mustbe frequently reducd by a dressing ,tool to-expose new cuttingsurfaces, which. is alaborious and expenslve operation.

To increase the efliciency of a porous wheel as above described it has been customai'y heretofore, to fill the pores of the wheel with a material that becomes soft and Specification of Letters Patent.

and thus Patented July'15, 1919.

Application filed lugust 27, 1918. Serial No. 251,844.

fluid at the grinding temperature. It is well known in the trade that a wheel so filled is more eflicient, for its pores do not clog or become loaded with the material bein ground during the grinding process.

The new substance which I have found useful for filling porous wheels herein described is a coal-tar distillate, known chemically as polymerized benzofuran or paracoumarone. Commercially it is sold under the names coumarone and paracoumarone, though these commercial products are practically identical in physical and chemical properties. This substance is spelled with the following names: coumaron, cumaron, cumarone, paracoumaron, paracoumarone, paracumarone.

The substance known chemically as benzofuran or coumarone is definite and has the formula C H O shown structurally thus 2-- ,mate product paracoumarone, and this is the substance, whether sold under the name paracoumarone or not, which I preferably use in my process, although I mav use paracoumarone of proper grade however it is obtained.

The structural formula of paraooumarone is shown as follows, being made up of two molecules of coumarone:

It is possible that more than two molecules unite to form even higher molecular aggregates.

, cut

There are severalcommercial ades of paracoumarone, some being high y refined and odorless, tasteless and almost colorless. Others have a characteristic light yellow to dark brown color. The grades; that are hard at ordinary temperatures are brittle. Others aretough and cold flowing at ordinary temperatures. The melting points of the differrades run from centigrade to 110 'centigrade. The specific gravity is about 1.1 in all grades. On heating, paracoumarone melts, gives a pleasant sweetish odor and on cooling again it is found to have lost noneof its former chemical and physical properties.

The coal-tar distillate, paracoumarone, is practically inert; it has no saponification number, no acid number, it is insoluble in alcohol, and dissolves readily in solvent naphtha. With an alkali it yields no lather. Furthermore, it oxidizes very slowly, even in the presence of strong oxidizing agents like nitric acid.

In the carrying out of my invention, I have found that the ordinary impregnating machines may beused. Briefly, the process consists in heating the porous wheel in a closed apparatus with the filler. The heat in coils at the bottom is turned on and at the same time the pressure inside the machine is reduced to a partial vacuum to 'facilitate the proper impregnation of the wheel with the fluid filler. It is essential that the filler become uniformly distributed. The process of impregnation usually occupics 25 minutes which is a suflicient length of time for practically all the voids of the wheel to becomefilled with paracoumarone. On removing the wheel is balanced while hot and on cooling the paracoumarone solidifies within the voids. The voids may be Wholly or partially filled with the paracoumarone, and the term filled as used herein and in the claims is to be so under- Having thus described and identified this coal-tar distillate which I use and having explained the process of adding it to the wheels I shall now explain the peculiar advantages resulting from its use in porous perature of grinding, due care must be given fo the melting point of the filler used in the pores of the wheel, If/ the grinding temperature is very high it is possible that the filler may become quite liquid long before the grinding temperature is reached. In such a case, the filler will run out of the wheel, the wheel will lose its balance, and acts as though it was softer, In fact, the filler has not accomplished any good purpose. This may be the case if thefiller is parafiin, a low melting grease, or other low melting substances. The coal-tar distillate, paracoumarone which I use is, on the contrary, a high melting substance. When certain grades are used, as high a temperature as 90 centigrade may be obtained before the material begins to flow. Such a substance does not melt too soon or before the grinding temperature is reached. Therefore, it does not leave the wheel and so performs its function in the wheel. Moreover, the wheel does not get out of balance and remains true to its grade or hardness.

If the grinding. operation is of such a naturc that a comparatively low temperature results, a corresponding low melting grade'of aracoumarone may be adopted as a filler. he wide range of melting points of the grades of paracoumarone is an advantage not to be found in the use of the-materials melting at only one definite temperature and hitherto used as fillers, (such as rosin, etc.).

Furthermore, my invention results in a wheel of greater efiiciency apart from the advanta- 5 already described. The filler, as it me ts, has a lubricating action on the cutting points of the wheel in their process of removin the material being ground.

Having t us described my invention, what I claim as new and desire to secure by Letters Patent is: I I

1. An abrasive wheel comprising abrasive particles united by a silicatejbinder to form a porous structure, and having the voids thereof filled with the coal-tar distillate my hand.

HENRY ROBERT POWER. 

